1. Field of the Invention
The present invention relates generally to magnetic heads for reading data written to storage media, and more particularly to magnetic read heads for disk drives.
2. Description of the Prior Art
As the areal density increases, and track widths become smaller and smaller, the difficulty of reading a particular track without interference or “cross-talk” from adjacent tracks increases. This occurs when the read sensor picks up magnetic flux from neighboring tracks, which then interferes with detection of data from the track currently being read. In an effort to decrease this interference, in-stack biased read heads which are configured with the current-perpendicular-to the plane (CPP) magnetic tunnel junction (MTJ) or giant magneto-resistive (GMR) sensors are often shielded with a side draped shield structure to minimize pick-up from adjacent tracks. These side drapes pick up the stray magnetic flux from neighboring tracks and route it away from the read sensor, so there is less interference. As shown in FIG. 5 (prior art), the read sensor 50 is generally sandwiched between a first shield S1 30 and a second shield S2 34. The side drapes 62 extend part of the S2 shield 34 downwards around the read sensor 50, and generally adjacent to the sensor 50, separated by a thin insulating dielectric spacer 69. The adjacent edge of this draped S2 structure 62 is typically configured with an abrupt edge 65. In practice this edge may have a finite slope and an edge that is not perfectly sharp. However, the magnetic domains 66, 68 in magnetic metal of this structure 62 are expected to be formed in parallel, but opposite orientations, as shown in FIG. 6 (prior art), which is a detail view of the side drapes, showing these magnetic domains. In such a structure, there is a natural tendency for the material to form a “closure domain” 64 at the sharp edge 65, by which a magnetic domain 64 spontaneously forms at right angles to the opposite but parallel domains 66, 68. This closure domain 64 thus acts to complete the magnetic circuit. However, this closure domain 64, where the magnetization direction is parallel to the field coming from the media, has lower magnetic permeability than domains where the magnetization is perpendicular to the field, and thus is less able to direct interfering magnetic flux from adjacent tracks away from the read sensor 50. It therefore provides less desirable magnetic shielding than a structure which does not include these closure domains.
Thus there is a need for a read head with draped shield structure in which the draped shield structure does not contain closure domains at the edge boundaries.